A conceptual model is a type of diagram that can be used to illustrate entities and relationships between entities. For example, a class diagram is a type of conceptual model that can illustrate software classes and associations between the software classes. As another example, an entity relationship diagram can illustrate database entities and relationships between the entities. Relationships can be illustrated, for example, as a connector, such as a line, that connects two related entities. A connector can include cardinality information that includes how many instances of a first entity may be associated with a related entity.